<mat-form-field appearance="fill">
  <mat-label>Custom calendar header</mat-label>
  <input matInput [matDatepicker]="picker">
  <mat-datepicker-toggle matSuffix [for]="picker"></mat-datepicker-toggle>
  <mat-datepicker #picker [calendarHeaderComponent]="exampleHeader"></mat-datepicker>
</mat-form-field>
